CVE-2025-11680: Out-of-bounds Write in libwebsockets PNG parsing

Severity: medium (CVSS 5.9 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-10-20 · updated 2026-10-08
Weakness: CWE-787

Description

Out-of-bounds Write in unfilter_scanline in warmcat libwebsockets allows, when the LWS_WITH_UPNG flag is enabled during compilation and the HTML display stack is used, to write past a heap allocated buffer possibly causing a crash, when the user visits an attacker controlled website that contains a crafted PNG file with a big width value that causes an integer overflow which value is used for determining the size of a heap allocation.

Affected products

warmcat libwebsockets: from 4.0 through 4.4.2; from 4.0 through 4.3.6

References

https://libwebsockets.org/git/libwebsockets/commit?id=2b715249f39291c86443b969a1088d59b6a89b78
https://www.nozominetworks.com/labs/vulnerability-advisories-cve-2025-11680

Get alerted when CVE-2025-11680 or the next vulnerability affects your stack